1. Field of the Invention
The present invention relates to a discharging device, or particularly to a discharging device for the photoconductor drum to erase the latent image remaining on the surface of the photoconductor drum by means of the discharge lamps.
2. Description of the Prior Art
An example of the conventional discharging device for the photoconductor drum is shown in FIGS. 3 and FIG. 4. For a discharging device 51 shown in FIG. 4, both longitudinal direction ends of a discharge lamp block 2 with several discharge lamps are attached to a mounting plate 53 with the screw 54. In building the discharging device 51 in a copying machine, the mounting plate 53 should be attached to a cleaning unit 30 so as to make the discharge lamp block 2 position between a main charger 20 and the cleaning unit 30 as shown in FIG. 3.
After removal of the toner remaining on a photoconductor drum 10 with the cleaning unit 30, the latent image remaining on the surface of the photoconductor drum 10 is erased by radiation of the light in a field (b) corresponding to the discharge lamp block 2. Successively the surface of the photoconductor drum 10 is charged uniformly by means of the corona discharge in a field (a) corresponding to the main charger 20.
For the discharging device 51 mentioned above, the temperature of the discharge lamp block 2 must become high to some degree owing to the exothermic reaction from the discharge lamps or from another heat source, for instance, a fusing roller possessed in the copying machine. So the thermal expansion of the discharge lamp block 2 in the longitudinal direction particularly becomes distinguished.
The discharge lamp block 2, however, could not expand at both ends in the longitudinal direction by some increasing length on account of its thermal expansion because it is attached at the foregoing both ends with the screws hitherto. For that reason, all over the discharge lamp block 2 is forced to flex. As the result, the distance between the photoconductor drum 10 and the discharge lamps differs by part in the longitudinal direction. The difference of the distance will be a cause of the potential nonuniformity on the surface of the photoconductor drum 10. The industrial-use wide copying machine especially shows the foregoing tendency greatly. Therefore the solution for such problems has been looked forward to.
Furthermore in the conventional discharging device 51 shown in FIG. 3, the field (a) and the field (b) of the photoconductor drum 10 according to the main charger 20 and the discharge lamp block 2 overlap sectionally, and are not partitioned distinctly as a straight boundary. Accordingly such an overlap of both fields (a), (b) will be another cause of the potentional nonuniformity.
Moreover the discharge lamp block 2 is deformed in the radial of the photoconductor drum 10 by the thermal strain in itself comprising as a complex of the plastic moldings and the electronic parts such as LED and so forth. So the above-said deformation will be still another cause of the potential nonuniformity.